In general, a semiconductor memory device includes a plurality of banks. A bank is a functional unit that can be accessed independently, and the bank includes a memory cell array, a sense amplifier array, an address decoder, and so on.
In general, in order to access a specific memory cell of a specific bank, first, a row (i.e., word line) of a corresponding bank is activated by applying an active command for controlling a row line. Next, sense amplification and re-storage processes are performed on a specific column (i.e., a bit line) by applying a read/write command for controlling a column line. When access to the corresponding bank is terminated, the row of the corresponding bank is deactivated by applying a precharge command.
A semiconductor memory device, in particular, Dynamic RAM (DRAM) performs a precharge operation for charging bit lines with a specific voltage in order to rapidly write and read data and close a bank of an active state.
In general, RAS active-time lookout (tRAM lookout or tRAM minimum time) using a clock outside a semiconductor memory device may be controlled by technology using a delay chain and an RC delay unit.
A conventional active control device may include an additional RC delay unit in each bank in order to control the delay operation of a normal RAS access time tRAS when a refresh operation is performed.
The conventional active control device may include a delay unit for delaying an RAS access time tRAS in a normal operation and a delay unit for delaying an RAS access time tRAS in a refresh operation in each bank, thereby increasing the total area of a control device.